Referanser CAEvirus

J Virol. 2004 Jul;78(14):7518-22.
Direct evidence for natural transmission of small-ruminant lentiviruses of subtype A4 from goats to sheep and vice versa.
Shah C, Huder JB, Boni J, Schonmann M, Muhlherr J, Lutz H, Schupbach J.
Swiss National Center for Retroviruses, University of Zurich, Zurich, Switzerland.

Small-ruminant lentiviruses (SRLV), which include the caprine arthritis-encephalitis and the maedi-visna virus, cause persistent inflammatory infections in goats and sheep. SRLV are mainly transmitted from mother to offspring through milk. Transmission after prolonged contact between adult animals has also been observed. The observation that certain SRLV subtypes are found in both goats and sheep suggests that interspecies transmission has occurred on several occasions in the past. We investigated seropositive goats and sheep that were kept together in small mixed herds. Phylogenetic analysis of long proviral sequences in gag and pol, combined with epidemiologic information, demonstrated natural sheep-to-goat transmission of the recently identified SRLV subtype A4 in two instances and goat-to-sheep transmission of the same subtype in one instance. In a further mixed cluster, the direction of the interspecies transmission could not be determined. These findings present for the first time direct evidence that natural interspecies transmission of SRLV is ongoing in both directions. The findings are of relevance to virus eradication programs in both species.

Vet Microbiol. 2004 Jul 14;101(3):199-208.
Transmission of small ruminant lentiviruses.
Blacklaws BA, Berriatua E, Torsteinsdottir S, Watt NJ, de Andres D, Klein D, Harkiss GD.
Department of Clinical Veterinary Medicine, University of Cambridge, Madingley Road, Cambridge CB3 0ES, UK.

Small ruminant lentiviruses (SRLV) are classical slow retroviruses causing chronic inflammatory disease in a variety of target organs. The routes of transmission have been investigated and a large body of evidence has accumulated over many years. The main routes are through ingestion of infected colostrum and/or milk, or through inhalation of respiratory secretions. However, many studies also provide evidence that intrauterine infection may occur, though the extent and significance of this route is controversial. Embryos treated to IETS standards appear to pose very little risk of infection. SRLV have been detected in semen suggesting a potential source of transmission. However, such transmission has not been demonstrated to date. The application of control measures based on this information allows more efficient strategies to be developed which will reduce the rate of transmission.

Virology. 2004 Feb 5;319(1):12-26.

Phylogenetic analysis and reclassification of caprine and ovine lentiviruses based on 104 new isolates: evidence for regular sheep-to-goat transmission and worldwide propagation through livestock trade.
Shah C, Boni J, Huder JB, Vogt HR, Muhlherr J, Zanoni R, Miserez R, Lutz H, Schupbach J.
Swiss National Center for Retroviruses, University of Zurich, Zurich, Switzerland.

We performed a phylogenetic analysis of caprine and ovine lentiviruses using long sequences in gag and pol of 104 new Swiss isolates and six available corresponding database sequences. Forty-five isolates, forming five sequence clusters, were unclassifiable by the present classification. Pairwise DNA distance analysis indicated different categories of relatedness, requiring a new classification system. We propose four principal sequence groups, A-D, which differ by 25-37%. Groups A and B are further divided into subtypes which differ by 15-27%. Group D and four of the seven group A subtypes, A3, A4, A5 and A7, are formed by new Swiss isolates. Molecular epidemiology revealed that Swiss B1 strains differed no more from French, Brazilian or US strains than from each other, suggesting virus propagation through international livestock trade. Furthermore, infection of goats by subtypes A3 or A4 was significantly associated with documented contact with sheep, which also harbor these subtypes, thus indicating regularly occurring sheep-to-goat transmission.

Small ruminant lentiviruses (SRLV = maedi-visna in sheep and caprine arthritis encephalitis in goats) are distributed throughout most countries of the world, particularly Europe. Laboratories from 16 European countries established collaborations within the framework of a COST (CO-operation in the field of Scientific and Technical Research) action sponsored by the European Union in order to (i) better organize their research programmes on SRLVs and (ii) to coordinate efforts to combat these two diseases. After five years, a consensus conference--the first one in the veterinary medicine field--concluded the work of this network of laboratories by reviewing the present position and discussing three important questions in the field of SRLVs: routes of transmission, consequences of infection and potential role of eradication programmes at either a European or local level, according to the situation in each country or region. This paper brings together existing information regarding these questions and identifies areas for future research. Copyright 2004 INRA, EDP Sciences